Various earth-boring tools such as rotary drill bits (including roller cone bits and fixed-cutter or drag bits), core bits, eccentric bits, bicenter bits, reamers, and mills are commonly used in forming bore holes or wells in earth formations. Such tools often may include one or more cutting elements on a formation-engaging surface thereof for removing formation material as the earth-boring tool is rotated or otherwise moved within the bore hole.
For example, fixed-cutter bits (often referred to as “drag” bits) have a plurality of cutting elements affixed or otherwise secured to a face (i.e., a formation-engaging surface) of a bit body. Such cutting elements generally have either a disk shape, or in some instances, a more elongated, substantially cylindrical shape. FIG. 1 illustrates an example of a conventional cutting element 100. The cutting element 100 includes a layer of superabrasive material 105 (which is often referred to as a “table”), such as mutually bound particles of polycrystalline diamond, formed on and bonded to a supporting substrate 110 of a hard material such as cemented tungsten carbide. The table of superabrasive material 105 includes a front cutting face 115, a rear face (not shown) abutting the supporting substrate 110, and a peripheral surface 120. During a drilling operation, a portion of a cutting edge, which is at least partially defined by the peripheral portion of the cutting face 115, is pressed into the formation. As the earth-boring tool moves relative to the formation, the cutting element 100 is drug across the surface of the formation and the cutting edge of the cutting face 115 shears away formation material. Such cutting elements 100 are often referred to as “polycrystalline diamond compact” (PDC) cutting elements, or cutters.
During drilling, cutting elements 100 are subjected to high temperatures, high loads, and high impact forces. These conditions can result in damage to the layer of superabrasive material 105 (e.g., chipping, spalling). Such damage often occurs at or near the cutting edge of the cutting face 115 and is caused, at least in part, by the high impact forces that occur during drilling. Damage to the cutting element 100 results in decreased cutting efficiency of the cutting element 100. In severe cases, the entire layer of superabrasive material 105 may separate (i.e., delaminate) from the supporting substrate 110. Furthermore, damage to the cutting element 100 can eventually result in separation of the cutting element 100 from the surface of the earth-boring tool to which it is secured.
As shown in FIG. 1, it has been found that the incidence of damage to the cutting element 100 may be reduced by beveling the cutting edge of the cutting face 115 to provide an angled, arcuate surface or “chamfer” 125 along at least a portion of the periphery of the layer of superabrasive material 105. In other words, a chamfered edge 125 may be formed for durability and long-term cutting efficiency. Conventionally, the chamfered edge 125 is formed by mechanical processes, such as lapping and grinding processes. Such conventional mechanical processes are historically prone to generating residual and subsurface microscopic damage. The damage is a result of the mechanical means by which a surface is abrasively manufactured and can only be minimized, not eliminated, through successively finer polishing steps. Such residual microfractures can remain at, and even beneath, the polished surface. These residual defects can propagate under the severe cutting stresses and loads into longer or larger defects, leading ultimately to the aforementioned spalling and delamination of the superabrasive material layer 105.
Additionally, in order to provide an improved finish (i.e., a more polished surface), an increasing number of polishing steps are required, which proportionally increases the amount of time required, and the attainable increments of finish improvement using conventional techniques are limited. Further, the high number of required steps for achieving a fine, polished finish cannot be reduced by applying a fine polish directly to a very rough surface. Indeed, attempting to achieve a fine polished surface directly from a very rough surface of a hard material will actually take longer than first achieving an intermediate finish prior to a fine finish.